neqsim-physics-explanations

neqsim-physics-explanations is a skill for Claude Code, Codex from equinor/neqsim. It costs 53 tokens per session (2,480 once invoked), scanned A, original, Apache-2.0.

A plain-language reference for explaining common NeqSim physics and thermodynamic results, such as cooling through a valve or liquid forming as pressure falls.

In plain words
What is it for?
Use it when someone asks why a simulated pressure, temperature, phase change, hydrate risk, or other physical result behaves unexpectedly.
Why use it?
It helps turn unexpected simulation behaviour into understandable explanations that can be used in reports, notebooks, and technical discussions.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when someone asks why a simulated pressure, temperature, phase change, hydrate risk, or other physical result behaves unexpectedly.

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Install with agentmods
npx agentmods add skills/equinor/neqsim/neqsim-physics-explanations
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add equinor/neqsim --skill neqsim-physics-explanations
Clone the repo
git clone --depth 1 https://github.com/equinor/neqsim

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for neqsim-physics-explanations

README.md
[![agentmods](https://agentmods.dev/badge/skills/equinor/neqsim/neqsim-physics-explanations/github.svg)](https://agentmods.dev/skills/equinor/neqsim/neqsim-physics-explanations)
Your own site
<a href="https://agentmods.dev/skills/equinor/neqsim/neqsim-physics-explanations"><img src="https://agentmods.dev/badge/skills/equinor/neqsim/neqsim-physics-explanations/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for neqsim-physics-explanations

Your own site · 80×15
<a href="https://agentmods.dev/skills/equinor/neqsim/neqsim-physics-explanations"><img src="https://agentmods.dev/badge/skills/equinor/neqsim/neqsim-physics-explanations.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 53 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,480 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00053 $0.02480
Opus 5 $0.00026 $0.01240
Sonnet 5 $0.00011 $0.00496
Haiku 4.5 $0.00005 $0.00248

Measured 7d ago against content hash 2954175257f0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

neqsim-physics-explanations scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/skills/neqsim-physics-explanations/SKILL.md · 164 lines

How it starts

The opening of the file, as written. The whole thing — 164 lines — stays where its author put it; the contents beside it link to each section on GitHub.

NeqSim Physics Explanations

Reference explanations for common thermodynamic and process phenomena. Use these to add educational context to simulation results.

Thermodynamic Phenomena

Joule-Thomson Effect

What happens: Gas cools when throttled (expanded through a valve) without doing work. Why: At moderate pressures, intermolecular attraction dominates — expanding gas molecules must overcome attractive forces, consuming internal energy, which lowers temperature. At very high pressures (above the inversion temperature), repulsive forces dominate and the gas heats up instead. Typical values: Natural gas JT coefficient: 0.3-0.7 K/bar. CO2: 0.5-1.2 K/bar (higher because stronger intermolecular forces). Hydrogen: negative (heats on expansion at ambient T). Engineering significance: JT cooling across choke valves can cause hydrate formation, wax deposition, or auto-refrigeration below material design temperature limits (MDMT).

Retrograde Condensation

What happens: A gas mixture forms liquid when pressure decreases (opposite of what you'd expect — normally, lowering pressure should vaporize liquid). Why: For mixtures between the cricondenbar and the cricondentherm on the phase envelope, the dew point curve has a retrograde region where the mixture enters the two-phase zone upon depressurization. This occurs because heavier components become less soluble in the lighter gas phase at intermediate pressures. Engineering significance: Rich gas/condensate pipelines may form liquid slugs during depressurization. Separator design must account for liquid dropout at pipeline conditions.

Hydrate Formation

What happens: Water molecules form cage-like crystalline structures around small gas molecules (methane, ethane, propane, CO2, H2S) at high pressure and low temperature. Why: At high pressure, gas molecules are forced close to water molecules. Below a certain temperature (the hydrate equilibrium temperature), the water cages become thermodynamically stable. The structure type depends on the guest molecule size: sI (methane, CO2), sII (propane, i-butane), sH (large molecules with help gas). Prevention: (1) Keep temperature above hydrate equilibrium + margin (typically 3-6 C), (2) Inject thermodynamic inhibitors (MEG, methanol) to shift equilibrium, (3) Inject low-dosage hydrate inhibitors (kinetic inhibitors, anti-agglomerants), (4) Insulate pipelines, (5) Remove free water (dehydration).

Read the full file on GitHub · 164 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 7d ago First seen · 164 lines · 53 tokens per session scan A 2954175257f0

Subscribe to this mod's changes

neqsim-physics-explanations is a skill published in the GitHub repository equinor/neqsim (151 stars, last pushed today), licensed Apache-2.0. It adds 53 tokens to every session and 2,480 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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